Abstract
Temporal variability in primary productivity can change habitat quality for consumer species by affecting the energy levels available as food resources. However, it remains unclear how habitat-quality fluctuations may determine the dynamics of spatially structured populations, where the effects of habitat size, quality and isolation have been customarily assessed assuming static habitats. We present the first empirical evaluation on the effects of stochastic fluctuations in primary productivity—a major outcome of ecosystem functions—on the metapopulation dynamics of a primary consumer. A unique 13-year dataset from an herbivore rodent was used to test the hypothesis that inter-annual variations in primary productivity determine spatiotemporal habitat occupancy patterns and colonization and extinction processes. Inter-annual variability in productivity and in the growing season phenology significantly influenced habitat colonization patterns and occupancy dynamics. These effects lead to changes in connectivity to other potentially occupied habitat patches, which then feed back into occupancy dynamics. According to the results, the dynamics of primary productivity accounted for more than 50% of the variation in occupancy probability, depending on patch size and landscape configuration. Evidence connecting primary productivity dynamics and spatiotemporal population processes has broad implications for metapopulation persistence in fluctuating and changing environments.
Highlights
Ecosystem functioning, understood as the pools and fluxes of matter and energy produced at the ecosystem level, has been claimed to play a key regulatory role in primary consumer populations by determining the net energy flux input into trophic webs [1]
We evaluated metapopulation responses to ecosystem fluctuations using generalized linear mixed models (GLMM) with binomial distribution and model selection protocols based on the Akaike information criterion (AIC) [38,39]
Our results reveal the importance of monitoring ecosystem phenology from remote sensing for tracking habitat quality fluctuations in relation to trophic limitation, an idea that is supported by increasing evidence connecting directly spectral vegetation indices with the diet quality and composition of herbivores [51]
Summary
Understood as the pools and fluxes of matter and energy produced at the ecosystem level, has been claimed to play a key regulatory role in primary consumer populations by determining the net energy flux input into trophic webs [1]. We assessed the effect of the connectivity index on patch occupancy dynamics by comparing models with and without S0iðtÀ1Þ: in order to test for the specific effect of primary productivity fluctuations on connectivity we tested competing models where this ‘dynamic-habitat’ connectivity index S0iðtÀ1Þ was replaced by a ‘static-habitat’ index S0iðmÞ in which p0jðtÞ was set constant The latter represents a situation where the contribution of sources only depended on their size and spatial distribution and not on variations in primary productivity. Pseudo-R2 statistics were estimated as an approximate measure of the model’s goodness of fit, separating the marginal component (i.e. variability explained by the fixed factors; R2ðmÞ) and the conditional component (i.e. variability explained by both fixed and random factors; R2ðcÞ) [47]
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